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## org.bouncycastle.crypto.engines
Class Salsa20Engine

    java.lang.Object
      org.bouncycastle.crypto.engines.Salsa20Engine

All Implemented Interfaces:
  SkippingCipher, SkippingStreamCipher, StreamCipher

Direct Known Subclasses:
  ChaCha7539Engine, ChaChaEngine, XSalsa20Engine

public class Salsa20Engine
extends java.lang.Object
implements SkippingStreamCipher

Implementation of Daniel J. Bernstein's Salsa20 stream cipher, Snuffle 2005

Field Summary
`static int` | `DEFAULT_ROUNDS`
`protected int[]` | `engineState`
`protected int` | `rounds`
`protected static byte[]` | `sigma` Deprecated.
`protected static byte[]` | `tau` Deprecated.
`protected int[]` | `x`

Constructor Summary
`Salsa20Engine()` Creates a 20 round Salsa20 engine.
`Salsa20Engine(int rounds)` Creates a Salsa20 engine with a specific number of rounds.

Method Summary
`protected void` | `advanceCounter()`
`protected void` | `advanceCounter(long diff)`
`protected void` | `generateKeyStream(byte[] output)`
`java.lang.String` | `getAlgorithmName()` Return the name of the algorithm the cipher implements.
`protected long` | `getCounter()`
`protected int` | `getNonceSize()`
`long` | `getPosition()` Return the current "position" of the cipher
`void` | `init(boolean forEncryption, CipherParameters params)` initialise a Salsa20 cipher.
`protected void` | `packTauOrSigma(int keyLength, int[] state, int stateOffset)`
`int` | `processBytes(byte[] in, int inOff, int len, byte[] out, int outOff)` process a block of bytes from in putting the result into out.
`void` | `reset()` reset the cipher.
`protected void` | `resetCounter()`
`protected void` | `retreatCounter()`
`protected void` | `retreatCounter(long diff)`
`byte` | `returnByte(byte in)` encrypt/decrypt a single byte returning the result.
`static void` | `salsaCore(int rounds, int[] input, int[] x)` Salsa20 function
`long` | `seekTo(long position)` Reset the cipher and then skip forward to a given position.
`protected void` | `setKey(byte[] keyBytes, byte[] ivBytes)`
`long` | `skip(long numberOfBytes)` Skip numberOfBytes forwards, or backwards.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

### DEFAULT_ROUNDS

    public static final int DEFAULT_ROUNDS

See Also:
  Constant Field Values

### sigma

    protected static final byte[] sigma

  Deprecated.

### tau

    protected static final byte[] tau

  Deprecated.

### rounds

    protected int rounds

### engineState

    protected int[] engineState

### x

    protected int[] x

Constructor Detail

### Salsa20Engine

    public Salsa20Engine()

  Creates a 20 round Salsa20 engine.

### Salsa20Engine

    public Salsa20Engine(int rounds)

  Creates a Salsa20 engine with a specific number of rounds.

Parameters:
  `rounds` - the number of rounds (must be an even number).

Method Detail

### packTauOrSigma

    protected void packTauOrSigma(int keyLength,
                                  int[] state,
                                  int stateOffset)

### init

    public void init(boolean forEncryption,
                     CipherParameters params)

  initialise a Salsa20 cipher.

  Specified by:
    `init` in interface `StreamCipher`
  Parameters:
    `forEncryption` - whether or not we are for encryption.
    `params` - the parameters required to set up the cipher.
  Throws:
    `java.lang.IllegalArgumentException` - if the params argument is inappropriate.

### getNonceSize

    protected int getNonceSize()

### getAlgorithmName

    public java.lang.String getAlgorithmName()

  Description copied from interface: `StreamCipher`
  Return the name of the algorithm the cipher implements.

  Specified by:
    `getAlgorithmName` in interface `StreamCipher`
  Returns:
    the name of the algorithm the cipher implements.

### returnByte

    public byte returnByte(byte in)

  Description copied from interface: `StreamCipher`
  encrypt/decrypt a single byte returning the result.

  Specified by:
    `returnByte` in interface `StreamCipher`
  Parameters:
    `in` - the byte to be processed.
  Returns:
    the result of processing the input byte.

### advanceCounter

    protected void advanceCounter(long diff)

### advanceCounter

    protected void advanceCounter()

### retreatCounter

    protected void retreatCounter(long diff)

### retreatCounter

    protected void retreatCounter()

### processBytes

    public int processBytes(byte[] in,
                            int inOff,
                            int len,
                            byte[] out,
                            int outOff)

  Description copied from interface: `StreamCipher`
  process a block of bytes from in putting the result into out.

  Specified by:
    `processBytes` in interface `StreamCipher`
  Parameters:
    `in` - the input byte array.
    `inOff` - the offset into the in array where the data to be processed starts.
    `len` - the number of bytes to be processed.
    `out` - the output buffer the processed bytes go into.
    `outOff` - the offset into the output byte array the processed data starts at.
  Returns:
    the number of bytes produced - should always be len.

### skip

    public long skip(long numberOfBytes)

  Description copied from interface: `SkippingCipher`
  Skip numberOfBytes forwards, or backwards.

  Specified by:
    `skip` in interface `SkippingCipher`
  Parameters:
    `numberOfBytes` - the number of bytes to skip (positive forward, negative backwards).
  Returns:
    the number of bytes actually skipped.

### seekTo

    public long seekTo(long position)

  Description copied from interface: `SkippingCipher`
  Reset the cipher and then skip forward to a given position.

  Specified by:
    `seekTo` in interface `SkippingCipher`
  Parameters:
    `position` - the number of bytes in to set the cipher state to.
  Returns:
    the byte position moved to.

### getPosition

    public long getPosition()

  Description copied from interface: `SkippingCipher`
  Return the current "position" of the cipher

  Specified by:
    `getPosition` in interface `SkippingCipher`
  Returns:
    the current byte position.

### reset

    public void reset()

  Description copied from interface: `StreamCipher`
  reset the cipher. This leaves it in the same state it was at after the last init (if there was one).

  Specified by:
    `reset` in interface `StreamCipher`

### getCounter

    protected long getCounter()

### resetCounter

    protected void resetCounter()

### setKey

    protected void setKey(byte[] keyBytes,
                          byte[] ivBytes)

### generateKeyStream

    protected void generateKeyStream(byte[] output)

### salsaCore

    public static void salsaCore(int rounds,
                                 int[] input,
                                 int[] x)

  Salsa20 function

  Parameters:
    `input` - input data

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